Hydraulic control system for excavating cranes



HYDRAULIC CONTROL SYSTEM FOR EXCAVATING .CRANES J. D.- HALE 'Alil 22, 1944.

Filed Feb.

5, 1940 s Sheets- Sheet 1 z INVENTQR,

v'I'IIIIIIIIIIIIIII I I I III. I -I'.

BY v I ATTORNEY.

Aug. 22, .1944. J. D. HALE v 2,356,517

-' HYDRAULIC CONTROL SYSTEM EXCAVATING CRANES Filed Feb. 5, 1940 8 Shasta-Sheet 2 8* Fe 2' (I V V W0 RETRAcr I J. D. HALE 2,356,517 HYDRAULIC CONTROL SYSTEM FOR EXCAVATING CRANES I I Aug. 22, 1944.

Filed Feb. 5. 1940 HYDRAULIC CONTROL $YSTEM FOR EXCAVATING CRANES Fil ed Feb. -5, 1940 8 Sheets-Sheet 4 Aug. 22, 1944. J. D. HAL'E' 5 5 7 HYDRAULIC CONTROL SYSTEM FOR EXCAYATING CRANES Filed Feb 5, i940 a sheets-sheets INVENTOR.

Aug. 22, 1944. J. D. HALE 2,356,517

HYDRAULIC CONTROL Y SZTEM FOR EXCAVATING CRANES Filed Feb. 5. 1940 8 Shee'tSrShe etj ATTORNEY.

Aug. 22, .1944;

J.' D. HALE HYDRAULIC CONTROL SYSTEM FOR EXCAVATING CRANES Filed Feb. I 5. l940 8 Sheets-Sheet 8 efforts have been satisfactory properties of the mechanical control systems of varying the operator cision in spotting.

Patented Aug.'2g, 1944 maa'u mo com-nor. SYSTEM FOR. EXOAVATING cams John 1). Hale, Milwaukee, Harnischfeger Corporation,

Wia, minor to Milwaukee, Wis.,' a

corporation of Wisconsin Application February '5, 1940, Serial No. 317,335

3 Claims. (of. Bil-54.6)

This invention relates to systems for'control' of friction-driven excavating cranes and resides. in an arrangement of friction members which are subject to control by hydraulic pressuie-,-

. generating means located at the control position occupied by the operator, the said invention speciflcally residing in a plurality of manuallyactuatable pressure-generating units so grouped and located with reference to one another and with reference to the crane body that the operator may, with normal, natural, and easily exeouted movements, and with moderate eflort, cause the engagement and disengagement of the several clutches and brakes which cause theexcavating crane to execute the usual excavating movements.

Heretofore in the art in excavating cranes,

made to overcome certain unlinkages heretofore employed, by substituting therefor means for transmitting control impulses from the operator brake to be controlled, by means of hydraulic forms. In all such hydraulic control systems heretofore employed, hydraulic pressure for actuating the same has been derived from a common reservoir or prime mover and control impulses have been transmitted by operator-controlled valving of pressure fluid. In the case of such systems an unduly complex arrangement of piping has been required, including circulating piping, supply and return piping, and the like. Furthermore, the valving arrangements employed with such systems are not well adapted to compactness and convenient location and have r not been adapted to grouping in such manner that the controls may be located for normal and natural manipulation by the operator. Furthermore, suchcontrol systems so completely deprive of the feel of the load that it is impossible to operate a machine equipped therewith without experiencing dangerous shock eifects and a certain amount. of wildness and lack of preto the particular clutch or tility is usually arranged to be driven ,in the forward direction by one friction clutch and in the reverse direction by another friction clutch and, in addition, is usually provided with a friction brake for arresting and holding the same. Such an excavating crane may be adapted in the wellknown manner for use either as an out-stroke shovel, as an in-stroke shovel, or as a dragline, by simple substitution of the necessary attachments therefor. As a result, the following primary digging controls are left swing, digging or brake. By custom, both directions of swinging movement are usually arranged to be under con-v forward digging or crowd, rearward trol of a single lever manipulated by the left hand ofthe operator, driving of the hoisting drum being under control by the right hand of the operatonwhile both forward and reverse rotation of the digging drum is controlled by a single lever placed between the hoist control lever and. the, swing control lever, so that it may bemanipulated by of the operator. In addition, control of the hoisting brake is regulated by a foot-pedal accessible tothe right foot of the operator, while control The friction-driven excavating crane as now manufactured is an apparatus of fairly well developed and crystallized design. Usually'there is provided a rotating cab, capable of free rotation in both directions. Mounted upon this rotating cab two principal drums are usually provided, one designated the hoisting drum arranged to be driven in the forward direction by afriction clutch, and also furnished with a friction brake for arresting and holding the same. The other principal drum is usually designated the "digging drum and for purposes of versa- M effective control is secured by forms of the embodiment of of the digging brake is regulated by a foot-pedal A accessible to the left foot ofthe operator. with out departing from the customary arrangement of controls, the apparatus of this invention permits the grouping of the same with unusually closeand convenient location with respect to the operator. In addition,

chanical linkages heretofore in use, positive and means of the apparatus of this invention with amount of travel. Furthermore, a reduction in the efiort required for operation may be achieved with the control of this invention. I

This invention is herein described with the aid of the accompanying drawings which form a part hereof and in which there is set forth by way of illustration and not this invention. In the drawings:

Fig. 1 is a. rear elevation, with parts broken away, of one form of control cabinet of this invention containing the pressure-generating elements of the apparatus of this invention.

Fig. 2 is a side sectional view .of the control cabinet shown Fig. 31 a detailed view, in side elevation, of

'r *orrlcka required: right swing,

retract, digging brake, hoist and hoist I of a lever manipulated either hand because of the absence of a large part of lost motion exhibited by mea'materially reduced of limitation specific I in Fig. I, viewed through the broken plan indicated by the section line 2-2;.

' shown.

control, showing the over-center hold-in linkages; i

Fig. 4 is a detailed view, in side elevation, of the control lever and rocker arm for controlling the pressure generating. cylinders of the swing control, elements of .the apparatus of this inven- .to control thereby;

Fig. 8 is a detailed view, partly in section, of a suitable hydraulic actuator for the friction bands employedin the apparatus shown in Fig. 5;

Fig. 9 is a detailed view, in section, of a brake-e holding valve which may be employed in-conjunction with the apparatus of this invention;

Fig. 10 isa rear elevation of another form of control cabinet suitable for use in connection with l the apparatus of this invention, the same being adapted for servo operation of the pressure generating cylinders;

Fig. 11 is a plan view, partly in section, of fragments of the servo actuators for swing controland the hoist and dipper actuators contained in thecontrol cabinet shown in Fig. 10;

Fig. 12 is a detailed view of the linkages employed in connection with the hoist control of the apparatus shown in Fig. 10;'

Fig. 13 is a detailed view of the boom hoist control of the apparatus shown in Fig. 10; and d Fig. 14 is a detail of the swing control of the apparatus shown in Fig. 10.

In Fig! 5 of the drawings one suitable form of the apparatus of this invention is shown mounted upon and applied to the control of a typical excavating crane rotatingbase. Upon the base there is provided a hoisting drum I, mounted to be driven by the hoist clutch 2 and controlled by the hoist brake 3. In addition there is provided a digging drum 4, arranged to be driven, in one direction by crowd-clutch 5 and in the opposite direction by retract-clutch 6. A brake for arresting movement of the digging drum 4 is mounted as shown at I. To provide the necessary power for rotation of the rotating base, right and left swing clutches 8 and 9 are provided, as

Control impulses to be transmitted to the parts above named aregenerated in a control cabinet l positioned upon the rotating base in convenient location for access by the operator, as shown. Piping connections extending from the control cabinet Hi to the individual clutches, and brakes are brought together and carried through a protecting sheath II, as shown. Contained-within the control cabinet ID are rightand left-swing control handle l2 for controlling-the clutches 8 and 9, crowd and retract control handle |3 for control of forward and reverse drive of drum 4,

and hoistcontrol handle I! for controlling rotation of drum I The machine shown in Fig. l is but one instance of an excavating crane such as may be employed in connection with the apparatus of this invention. The machine as shown diagrammatically is mounted upon a suitable traveling base I 8, upon which there is mounted rotating trol instrumentalities. Extending from the rotating base I9 is a boom 29, upon which there is mounted, in well-known manner, the shipper shaft I4 for producing crowding and retracting movement of the dipper stick l5 under influence of the sprockets and chains indicated by dotted lines which communicate, as shown in Fig. 5, with the digging drum. 4 through the idler sprockets 2|. Outward action of the dipper is produced by hoisting line I, which is arranged to be wound upon hoist drum I.

In order to better describe theflapparatus by which control impulses are created and the manner in which the same is arranged for ready acldce'ss. by the operator, reference is had to Figs.

1, 2, 3, and 4 of the'drawings. As shown in these figures, a horizontal shaft 2| extends transversely across the interior of the upper part of control cabinet l0. Pivotally mounted upon the left end of shaft 2| is a rocker assembly 22 having oppositel'y extending rocker arms 23 and 24, as shown more clearly in Fig. 4. Formed as a portion of the rocker assembly 22 is an upwardly-' extending boss 25 to which there issecured the 25 swing-control lever 26, which terminates in handle l2, as'shown, for easy grasping by the operator. Mounted vertically above the extremity of the rocker levers 23 and 24, upon the shelf 21, are a pair of pressure-generatingcylinders of well-known form, such as are employed in'automotive hydraulic brake systems. One of these cylinders is designated by thenumeral 28, the other by the numeral 3| in Fig. 6, said cylinder being hidden in the other views in.the drawings but beingv of exactly similar form; Impulsetransmitting tubes 29 and-30 emerge respectively I from the cylinders 28 and 3I,-the same being shown partially broken away for clarity in the showing. Extending upwardly from the ends of the rocker arms 23 and 24 are a pair of pivotallyvconnected pushrods 32 and 33, which are secured to and extend through flexible boots, one of which is shown at 34, into the interior of their respective operating cylinders into engagement with a piston contained therein in a manner to be more part of a rocker assembly 31 pivoted to turn upon shaft 2|, as shown more in detail in Fig. 2. The rocker assembly 31 includes laterally-extending rocker arm 38 and depending rocker arm 39 and carries upon the side opposite the rocker arm 38 a pivotal idler link mounting 40. The lower end of depending rocker 39 makes pivotal connec-' tion, as shown, with thruster link 4|, which in turn engages the juncture between toggle links 42 and 43. The upper end of toggle link 42 is connected to and guided by an idler link 44, which is carried upon the idler link mounting 40, previously referred to. The lower end of toggle link 43 is provided with a. lost-motion slot, as shown, which engages a pin held by bracket 45, which is securely bolted to the back plate of cabinet III,

as shown. a

' Mounted above the rocker assembly 31 on the horizontal shelf 21 is a pair of pressure-generating cylinders 46 and 41, being in form exactly similar 7 to cylinders 28 and 3|, previously referred to.

, Pivotallyconnected to and extending upwardly 1 from the upper extremity of,toggle link 42 is a pushrod 48 which is secured to and passes upwardly through a flexible boot 49 in the interior of cab I8, containing the'various holstlnsa d 90!;- cylinder 41, where it engages a pressure-generat- 2,356,517 ing piston. In like manner, pivotally connected to and extending upwardly fromthe extremity of rocker arm 38 is a pushrod 50, which is secured to and extends upwardly through a flexible boot into engagement with a downwardly facing socket in piston 52, which is arranged to slide in cylinder barrel 53.

The pushrod 58 fits loosely in the socket in piston 52 so that when the lever 35 is moved in the directlon'designated Retract in Fig. 2, the piston 52 is raised in the cylinder barrel 53, causing arise in fluid-pressure therein, while, on the other hand, if the lever 35 be moved in the direction designated by the legend Crowd, the end of pushrod 58 simply separates from its seat in the socket in piston 52, while the piston 52 remains.

stationary in its lowermost position, as shown in Fig. 2, and while a corresponding extension in I boot 5| takes place. Communicating with the cyl-- inder barrel-53, as shown, isa reservoir 58, adapted 'to hold fluid and to compensate ,for leaks and losses which may occur. .A compression spring 55 within the cylinder barrel 53 assists in the return of the piston 52 and aid in retaining cupwasher 55. a

The foregoing described structural detail of cylinder 46 is characteristic of the structural detail of. cylinders 28, 3 I, and 41, which have already been referred to, as well as cylinders 51, 58, and 59, which will be hereinafter mentioned.

4 Upon movement of control lever 35 in the diin form similar to may be applied to the hoist drum I a cylinder 58,

scribed, is mounted lower rear wall of upon a bracket secured to the the cabinet I8. I A piston-actuatingpushrod 14 emerges from cylinder 58 and its flexible boot 15, the pushrod 14 being pivotally connected at its lower end to a rocker arm 16,.

which forms a part of bell-crank assembly 11, which in turn is mounted upon 18, secured to the rearwall upwardly extending rocker arm I9, which torm a part of the bell-crank assembly 11, makes pivotal Secured to the outlet of cylinder 58 in hydraulic.

communication therewith is a'check-valve and by-pass unit 81 which provides an unrestricted hydraulic passage from the cylinder 58 to the impulse-transmitting tube 88 when in the position shown in Figs. 1 and 2 of the drawings. Check- I valve and by-pass unit 81, however, i provided rectiohdesignated Crowd, toggle links 42 and 43 are caused to move toward a position of alignment, thus-forcing pushrod 48 into cylinder 41 .until the over-center position is reached. 133

moving the to gle links 42 and 43 slightly beyond,

the over-center position, the lever becomes self- 5 retaining, in which position it will remain until the operator desires to release it by a slight push toward rest position. Emerging from the pressure cylinders 46 and 41 are pressure-transmitting tubes 58 and 6 I, respectively, which are broken away for clarity in the showing and which emerge from the cabinet I0 through the grommet plate 62, as shown clearly in Fig; 2. I

To provide control for the driving of the hoisting drum I a lever 53 extends downwardly into engagement with a boss 84 which forms a part of i to turn upon, the

rocker assembly" 55- mounted shaft 2|, in the manner shown in detail in Fig. 3. The rocker assembly 55 is provided with a depending rocker arm 56, which pivotally engages a thrust link 51, which in turn pivotally joins with the midpoint of the pair of toggle links 68 and .59. The upper end of toggle link 68 is, guided by a pivotal idler link 10, which makes pivotal conwith an operating lever 89, which may be moved by drawing upon the knob 98 which is connected thereto by flexible operating wire 9I. When the control lever 89 is thus raised, check-valve and by-pass unit 81 provides a hydraulic passage for the fluid from cylinder 58 to transmitting tube as only in the outward directioii. The hoist brake may thus be rendered self-retaining by drawing knob 99', and said self-retainingcharacteristics may be released by returningthe knob 90 to the position shown. 1

The construction of check-valve "and by-pass unit 81 is like that of the unit 92, shown in detail a in Fig. 9, where the unit is shown as comprising assembly I82, adjustable link- I83, treadle rocker nection with the rocker assembly 55, as shown.

Pivotally connected to and extending upwardly from the upper extremity of toggle link 58 is a vertical pushrod 1 I which is'secured to and passes through a flexible boot 12 into-the interior of pressure-generating cylinder 51. Movement of the lever 63 in the direction designated by the legend "Hoist in Fig. 3 eventually brings the toggle links 58 and 69 to and beyond an over-center position, as shown by the dotted line inFig. 3. The hoist control is thus self-retaining in the position of extreme applied pressure, but maybe released. by a slight manual pressure in the return direction. A tube 'for transmitting control impulses gen- ;erated in the cylinder 51 emerges therefrom and is designated by the numeral 13, this tube being shown partially broken away, as in the case of tubes emerging from the other cylinders.

For the purpose of controlling the brake which by-pass plug'valve 93, which controlsby-pass and ball-check-valve 95, which controls the check-valve passage 96. Plug valve 93 is controlled by control lever 91, the position of which may be regulated by the knob 98 acting through flexible control wire 99. Unit 92 is employed in connection with cylinder 59 which is mounted ina manner similar to the mounting of cylinder 58 and is controlled through push-rod IIlI, rocker I84, and treadle pad I85, as shown. Control pressures createdin cylinder 59 and transmitted through unit 92 are transmitted into the com municating tubing I 08, as shown.

To provide for asupply of hydraulic fluid to makeup such losses as may occur and to maintain a slight hydrostatic pressure throughout the air, a central sup I07, shown in Fig. 6, is provided.

systemto prevent entrance of ply reservoir 7 The supply reservoir I01 is positioned slightly above the highest point of elevation of any of the parts of the hydraulic system and is connected to the individual reservoir of cylinders 5?, 55, 41, 28, 3|, 59 and 58, by means of a manifold tube I08, as shown.

' The control impulses created in the several pressure-generating cylinders may be converted into control action by any suitable means. One

of such means, adapted ,for the controlling of the band clutches and brakes shown'in- Fig.5, is shown in detail in Fig. 8. The actuator shown in Fig. 8 is adapted to cause contraction of a the cylinders previously de-- 1 a supporting shaft of cabinet I8. An

band I99 about the periphery of, a drum III]. Hydraulic, fluid fed into the center of cylinder barrel II6 between a pair of opposed, outwardly acting pistons III causes the upper 'ends of rocker arm II2 to move away from one another while pivoting about the fulcrumblocks II3,

which are held by the fulcrum bolt II4, thus causing the open ends of the band. I09 to-move toward one another. The band 109 is preferably restrained from tangential movement by a radially-displaceable anchoring link II 5. If desired,

however pressure cylinders of conventional form acting upon the thruster forks of other forms of clutches or brakes, such as clutches 8 and 9 employed to control swinging movement, may be employed as diagrammatically indicated in Fig. 6.

' From the foregoing it will be noted that means are provided by the apparatus of this invention through which the various operating functions of an excavating crane may be controlled without the use of the complicated system of mechanical linkages heretofore employed and without the complexities and diillculties of power-driven hydraulic control systems heretofore proposed. All

controlling members are conveniently located and accessible to the operatorand may be compactly aramged and positioned at the forward end of the operating cab without causing obstruction or inconvenience.

In the case of heavy machinery, where the effort of the operator alone is not adequate to perform the control work required, the apparatus of this invention may be adapted for servo-oper-- ation, as shown in Figs. 10, 11, 12, 13 and 14.

Such apparatus may be in all respects similar to with a laterally extending arm I29, the outer end of which is bored to-slidingly receive the reaction rod I30, shown clearly in Figs. 11, 12,

and 14. To eliminate any undue friction between the intermediate non-turning thrust member I24 and the driven clutch disk I25, bearing I3I is provided.

Driven clutch disk I25 carries a crank-pin I32 which. makes connection, as shown in Fig. 14,

with connecting-link I33, which in turn pivotally connects with the rocker I34, which rocker is mounted. to turn upon the rock-shaft I35. The opposite end of rocker arm I34 is pivotally connected, as shown in Fig. 14, with a pushrod I35, whichenters cylinder I IT to actuate a piston therein in the manner which has been previouslydescribed in connection with other pressuregenerating cylinders of the apparatus of this invention.

It will be observed, therefore, with the continuously running shaft II4 turning in a clockwise direction, as viewed from the right hand end,-

that engagement-of driven clutch disk I25, caused by movement of the swing-control lever II9, as described above, will cause the pushrod I35 to be forced into the'cylinder I", thus generating a hydraulicimpulse. It will be understood that the driven clutch disk'l25 is a continuouslysliding member and that the same is capable of that which has been described above with the exception that effort applied to the control memhers is derived through continuously sliding friction clutches arranged to be manipulatedby the operator. Power for the'operation of the sliding ,clutches may be derived through a single con- ,tinuously turning shaft II 4 mounted. in cabinet H5 and driven by sprocket II3, as shown in Fig.10.".

Containedwithin the control cabinet I5 isa pair of pressure-generating cylinders H5 and -I II, which are mounted-upon and held rigidly in place by channel member 0. These cylinders are arranged to be. connected by means not shown with therightand left-swing clutches of the crane, respectively, through tubes 29 and 30 shown in Fig. 6. The transmission of actuating forces to: the cylinders II 5 and III is controlled by .the operator through the swing-control handle I-I9. The swing-control handle II9, as shown 7 in Figs. 11 and 14, makes rigid connection with a thruster-hub I20, which in turn. is carried upon a double row thrust-bearing I2I, which locks the thruster-hub I20 against endwise movement along shaft II4, but which permits hub I20 to remain stationary, or turn, independently of the turning'movement of shaft II4. To the right of hub I20 is a pair of inclined cam faces I22, which become operative upon movement of the swingcontrol lever I I9 away from the operator to cause the non-turning intermediate thrust member I24 to. act toward" the right, thus causing driven clutch disk-I25 to be engaged and rotated by spring-backed driving clutch disk Ht-which is beingmontinuously driven by means of'the splined connection I21, which is carried aroundby the -continuously rotatingshaft II4. A plate-spring I23 furnishes desired resiliency to the driving clutch disk I29, as shown.

Intermediate thrust member I24 is provided a limited amount of rotation only by reason of thelinkages connected thereto. and, further, it

will be readily understood that the intensity of hydraulic impulse created thereby will be regulated by the intensity of, the pressure of engagement between driving disk I23 and driven disk I25, 9. factor which is entirely under the control impulse.

In like manner the crowd" and "retract control handle I43 is mounted upon continuouslyturning shaft H4 in proper relationship to control the crowd and retract'clutches designated generally by the numerals I44 and I45, respectively, which clutches, acting through linkages similar to those above described,'produce hydraulic impulses in ,crowd and "retract cylinders I 46 and I4Lrespectively.

Fluid impulse transmitting 6, may connect the cylinders I46 and I4! with "crowd and retract clutches.

To provide a control for the hoisting drum and to render said control self-retaining in the extreme applied position, hoist-control handle I49 is mounted upon a free-turning center disk I50 and associated with the remaining parts in a.

manner quite different than that which has been previously described. Disk I50 is capable of free turning movement independently of stationary side-thrust hub I49 and displaceable side-thrust hub I5I, although all of these parts derive support from and perform their functions independentlyof the turning of shaft II 4 by reason of double-row thrust bearing I52. As shown more clearly in Fig. -12, disk I50 is provided with a downwardly-projecting lug I53,.which pivotally.

conduits, not shown, such as conduits 50 and 6|, shown in Fig.

- is felt by the engages a pushrod I64, whichin turn is arranged to act upon the bell-crank I55, which is mounted to turn upon the reaction rod I36, as shown. The longer of the two unequal arms of the bellcrank l55 makes pivotal engagement with a clevis which is secured to the end of adjustable connectingfbolt I56, which bolt passes through a trunnion block I51, which is in cooperative engagement with the curved lug I58, which in turn is secured to the independently movable thrusterhub .II, as shown in Figs. 11 and 12. When the lever I48 is moved counter-clockwise the link I54 straightens the toggle links I55 and I18. This.

tends to cause the piston rod I 65 to enter the cylinder I61 however, at the same time the longer end of the toggle I55 pulls upon the. rod I56 and thus rotates the clutch thruster I58 causing the friction disks I61 and I62 to come into engage- 11. The intermediate thrust member In my be provided with an operating handle I13, upon the movement of which handle toward the operator driven clutch disk I14 comes into engagement with driving clutch disk I15, as shown. A connecting link I16, which engages a crank-pin mounted on the driven clutch disk-"41s ar ranged to operate a rocker I11, to the endof which rocker any appropriate means may be secured, such as-transmis'sion rod I18, which extends to the dipper trip or other instrumentality which it is desired-to operate, but which is not ment. Thereupon, the connecting rod I63 pulls on the lever I64 and thus contributes its force to cause the piston rod I65 to enter the cylinder I61. It will be apparent, therefore, that upon movement of the hoist-control lever I48 toward the operator, thruster-hub I5I will rotate so as to cause inclined cam faces I59 to act against nonturning intermediate thrust member I68, thus causing engagement of driven clutch disk I61 with driving clutchdisk I62. When this occurs, connecting link'l63, as shown in Fig. 12, will move so as to cause rocker I64 to turn, thus forcing pushrod I65 intocylinder I61. The resulting intensity of hydraulic impulse created in cylinder I61 as compared with the efiort applied to the lever I48 may be regulated through adjustment of adjustable nut I68 acting against adjusting spring I68 and thus the degree to which the load at the pleasure of the operator. The engaging force between the disks I6I and I62 is transmitted through the compression spring I68. Therefore it initial compression is setup in spring I68 by turning down the nut I68 a stronger force may be transmitted through it and if such is. done the clutch disks I6I and I62 engage with greater intensity and contribute in larger measure to the force required to drive the piston rod I65 into the cylinder I61. The part of the force con-- tributed for this .purpose by the efiort of the operator applied to the straightening of the toggle links I55 and I18 therefore is diminished and the higher the initial compression in spring I69, the less the operator has a feelot the load. It will be noted that at all times the operator has operator is subject to regulation a sense of the extent to which the piston rod I66 has enteredthe cylinder because of the direct linkage connection between the lever I48 and the piston rod I65. "Thus the operator can not only feel how hard a load is involved, but he may also sense to what extent movement under load has taken place.

In order that the hoist control may exhibit self-e retaining properties in the extreme applied position, a link I16, shown inFig. 12, is interposed between and pivotally connected to the rocker I and the rocker I64, thus forming a toggle linkage which will hold the control in applied position once said toggle linkage has been carried beyond the over-center position. The cylinder shown.

To provide for precise positioning of inclined cam faces so as to insure consistent engage-" ment of th sliding clutch disk, said cam faces, as shown,for example; in

Fig. 14, may be mount.-

ed upon members having-elongated tangential means about their periphery forapcommodation I19, which pass thereis possible to loosen the of theassembly bolts through. At any time it bolts I18 and reset the proper position, similar effects. I 1

If desired, manual controhnot assisted by any inclined cam faces in servo-action may be combined with the servo control above described, as, for example, shown in the case of boom-hoist control lever, I80, which is simply mounted to pivot'about shaft I I4 upon I the hub I8I, as shown. Projecting from the huh I BI is a lug I82 which engages connecting-rod I83, which acts through rocker I84 mounted on rockshaft I35 to cause manual actuation ofcyl inder I85, which cylinder, by appropriate piping connection, not shown. may be connected to at boom-hoist clutch.

In like manner and also without benefit of I servo-action, there may be included within the cabinet 6, foot-operated control, as shown. For example,'a crowd" and retract foot-brake I86, arranged to act upon the cylinder I81, in the manner described in connection with cabinet I8, may be provided and connected by' appropriate tubing, such as tube I06, shown in Fig. 6, with the, brake controlling the. "crowd and "retract or digging drum; If desired, a checkvalve and by-pass unit I88, controlled by the knob I88, may be interposed in such transmission tubing. In like manner, a hoist-drum brake I90, pressure cylinder I8I, by-pass and check valve unit I82 and control knob I93 may be provided and connected as shown in Fig. 6 with tubing 88 to provide brake control for the hoisting drum. If desired, there may also be provided a brake pedal I84, pressure-cylinder I85, by-pass and. check valve unit I86, and control knob I81, for control of the boom hoist I98, shown in Fig 7, through appropriate tubing connections not shown.

From the foregoing it will be observed that through this invention there is provided draulic control for machines of the type of the excavating crane, which control may be either i This is accomplished by providing separate pres I61 may be connected by tubing, not shown, to

the hoistingclutch as t the tube 13 shown in Fig. 6. V

To provide a servo-actuated dipper trip, an intermediate thrust member "I maybe mounted so as to act against non-turning thrust-hub I48, through inclined cam faces I12, as shown in Fig.

manually or power operated and which control eliminates the deficiencies of hydraulic control systems heretofore employed on excavating cranes wherein valving of fluid supply is involved.

sure-generating means for each control function required and by locating said pressure-generat-- ing means in close proximity to the member which is manipulated by the operator to cause energization thereof. By so doing mechanical linkages extending over great distances are avoided and all the advantages of ease of instalthus; compensating for wear andforces produced thereby. i

am of hydraulicotr'ansmission tubm arepats tained, while at the sametime retaining {close correspondence between the control 'eiiort exerted by the operator andthelre'sulting control While there has been herein specific instances of the embodiment of this invention; it

is desired that it be understood that -the'fsame are set iorth'by way of illustration and not 'otlimitation, since it is intended thatthe protection of Letters Patent to be granted hereon extend to 2. ,In a hydraulic control the combinatim comprising a pivoted control lever movable to and irom a rest position, a hydraulic cylinder having axpiston, continuously sliding controllable i'riction-driven means for causing said piston to en- ,ter said cylinder, 'a source of power for driving 1 the same, an-over center means movable toward and slightly beyond a. self-retaining over center position connected to saidcontrol'lever for movethe limits of the inventive advance disclosed herein as set forth in the claims hereto appended.

. .fi'hat which I wish to claim as my invention is: .1. In a hydraulic control, the combination comprising a pivotedcontrol lever movable to and from a rest position, a hydraulic cylinder having apiston, continuously sliding controllable frictiondriven means for causing said piston to enter said cylinder, a source' of power for driving the same, a pair of toggle links movable toward and slightly beyond a position of alignment connected to said control lever for movement thereby, means actuated by movement of said toggle links tor causing and controlling engagement of said continuously sliding friction-driven means with said source of power. and means engaging one of said toggle links and saidpiston whereby said control lever is rendered self-retaining in extreme appiston into said cylinder may be sensed by one operating saidcontrol lever.

ment thereby, means actuated 'by-movement of saidover center means for causing'and controlling engagement of said continuously sliding friction-driven means with said source of power, and

a connection between said control lever and said.

piston whereby the extent of movement of said piston into said cylinder may be sensed by one operating said control lever.

3. In a hydraulic control the combination comprising a movable control member, hydraulic dis placement means, continuously sliding controls lable friction-driven means adapted to act upon said hydraulic displacement means, a source 0! power for driving said friction-driven" means, means connecting said control member to said hydraulic displacement means, and resilient ad- Justable means associated with said connecting I means and adaptedto cause and control engageplied position and the extent of movement of said so ment of said continuously sliding friction-driven means with said source of power.

JOHN D. HALE. 

